1. Field of the Invention
This invention is related to closed circuit television and other observation cameras and their casing and to IR or other illuminators and their casings used for day-night observation of fences and other security installation.
2. Description of the Priort Art
Cameras for closed circuit television, network cameras and other digital cameras used for fence observation are mounted inside an outdoor housings on top of the fence's pole or post for observing the fence from top, whereby, the angle of view of the observed fence is determined by the lens, the height of the pole or post and the housing's vertical tilt and horizontal coordinates. Long fences, such as border fences between countries, are extended over mountains and valleys and are not structured in straight lines and the observation of the fences therefore, requires many compromises relating to the angle of view.
For example, the viewing of fence details calls for narrow-angle lens, which depicts the fence as a larger object onto the monitor screen, but which cuts portions of a fence section from the optical path of the camera and the viewed scene. On the other hand, the observation of a complete section of a fence such as between two poles calls for wider-angle lens, which depicts the fence on a monitor as a smaller object of a wider viewed area.
These two conflicting limitations, the observation of the fence details versus the observation of the entire section of a fence is a major compromise issue, whereby it calls for a consideration of giving up on fence details or allowing portion of the fence to be left unobserved.
Moreover, the lens' angle of view limitations are coupled with landscape limitations due to the terrain and the elevation of the poles or posts of the fence, as well as the bend sections or corners of a stretched fence, all of which greatly compels the positioning of the housing's tilt and pan coordinates in line with the landscape. This landscape limitation further inhibits or prevents altogether the viewing of a complete individual section between two poles of a given fence.
The unavoidable lens compromise and the positioning limitation of the housing pan-tilt coordinates, because of the landscape, regularly leaves portions of the fence uncovered by the surveillance cameras. These uncovered sections are known as blind stretches, blind sections or blind spots.
Further, camera and illuminator housings mounted on poles above the fence are prone to vandalism or destruction by intruders at distances far from the fence itself, thereby, increasing the risks of intruder defeating the fence observation system, particularly at night.